1. Field of the Invention
The present invention relates generally to hydrostatic transmission drive systems and more specifically to such systems which employ more than one transmission.
2. Description of the Prior Art
Hydrostatic transmission drive systems are well known in the prior art. It is common in such systems to extend the output speed range of the transmission by employing a variable displacement motor in the system whose displacement may be reduced to increase drive speed without further power demand. In such systems the displacement control mechanism of the motor is normally biased to the maximum displacement position by utilizing springs. Exemplary of such systems is that disclosed in U.S. Pat. No. 3,411,297. The use of such springs has an adverse effect on the manufacturing cost of such systems.
When two independent output drives are required in a particular application such as the drive-and-steer systems employed in tracked or skid steer type vehicles, displacement control of the motors is normally effected through manual selection by the operator. Since direction and speed of the drives is also typically manually selected, the demands on operator dexterity in operating such vehicles are great.